Record rain could mean isles entering wetter cycle

Hail on the Big Island. A twister on Lanai. Crumbling dams on Oahu and Kauai. Record rainfall across the state.

If the wild weather of recent weeks seemed like a once-in-a-lifetime event, there is a reason: Experts say the heavy rain and associated weirdness were caused by a rare weather scenario that last played out in the islands 55 years ago.

From late February through March, the weather systems that normally spin and flow around the globe became locked in a sort of global traffic jam that kept them in place across the entire Northern Hemisphere, said Andy Nash, director of operations for the National Weather Service's Honolulu office.

Called "blocking," such gridlock is not uncommon, occurring once or twice a year and causing weather systems to overstay their welcome for a week or so before things start moving again. But this one persisted for an unheard-of six weeks.

For Hawaii this meant that a low-pressure system in the western Pacific that would have otherwise moved on after a few days instead stayed put, and on Feb. 19 began flinging one rainstorm after another at the islands.

Heavy rain is nothing new here, but the repeated downpours waterlogged the soil in some areas, overtaxing its ability to absorb new rains.

"This type of thing is not unprecedented, but what was really unusual was the duration," said Nash.

We were not the only ones to suffer. Flooding raged in Central Europe as a rain system stayed put there. Texas sweltered under a dry spell. Californians suffered from torrential rains of their own.

National Weather Service hydrologist Kevin Kodama, who tracks rainfall around the state, said situations like this occurred "once in a career."

"At least that's the hope. We certainly don't want to see another like this again," he said, referring to the death and damage around the state.

The last time a comparable situation occurred here was in March 1951, when weather systems fell into the same pattern in the Pacific. Monthly or all-time rainfall records were set, many still standing in some areas of the islands.

But last month left its own mark on the record books.

Rainfall at Lihue Airport's gauge reached a record 36.13 inches in March, shattering the old monthly mark of 22.91 inches, set in December 1968.

Through the first three months of 2006, gauges at Lihue Airport and Port Allen on Kauai and at Honolulu Airport had already exceeded normal rain totals for the entire year.

"What happened last month set a new standard," Kodama said.

Whereas most of March normally is caressed by tradewinds, there were only five days of trades last month, against an eye-popping 22 days with flash-flood warnings.

Nash and his team plan to study what happened and whether there are ways to spot a recurrence.

However, he doubts whether bigger phenomena were at work. The current La Nina episode might have contributed to the blocking by weakening the jet stream, he said, but blaming global warming is a stretch.

But long-term climate data suggests the inclement weather could portend a wetter era ahead, said University of Hawaii meteorologist Pao-shin Chu, who also is Hawaii's state climatologist.

Rainfall patterns in the North Pacific alternate between wet and dry periods, each lasting roughly 28 years, Chu said. Rainfall was higher than normal from the mid-1940s to the early 1970s, when it fell off to below-average levels that persisted through the 1980s and '90s.

Chu said there are signs the drought might have bottomed out around the year 2000 and has begun inching back up, though he adds the trend will not become clear for several years.

"It seems like that's been happening that past couple of years -- but who knows for sure?" he said.